Phthalocyanine modified TiO2 or WO3-catalysts for photooxidation of sulfide and thiosulfate ions upon irradiation with visible light

The photooxidation of Na2S or Na2S2O3, catalyzed by Al2O3, TiO2 or WO3 superficially modified with metal-free phthalocyanine complex (Pc), cobalt phthalocyanine complex (CoPc) and copper phthalocyanine complex (CuPc), has been studied upon irradiation with visible light. The rates of the substrate photooxidation, catalyzed by the phthalocyanine complexes supported on TiO2 or WO3, are much higher than those registered with the same complexes, anchored on Al2O3. The high photocatalytic activity of the samples is explained by an electron transfer from the conduction band of the excited phthalocyanine semiconductor particles to the conduction band of the TiO2 or WO3 supports. The increase of the quantum yield of the photocatalytic redox process comes as a result of the additional formation of superoxide radicals on the TiO2 or WO3 conduction bands. A complete oxidation of Na2S or Na2S2O3 to sulfates has been registered in the presence of the studied photocatalysts. (C) 2003 Elsevier Science B.V. All rights reserved.